In recent years, there has been widely used non-contact IC tag which is attached to-be-controlled persons or goods (adherends) for control of the flow, circulation, etc. of such persons or goods. This IC tag can memorize data in the IC chip built therein. By allowing the IC tag to communicate in non-contact with an interrogator, the to-be-controlled data memorized in the IC chip can be exchanged with the interrogator.
As the application fields of IC tag, there are various fields, for example, communication tickets, control of human incoming or outgoing in business, stock control of goods, and control of physical distribution. IC tags of various forms have been produced so as to match such application fields.
Throw-away IC tag is fitted to, for example, goods and are placed at a shop together with the goods; when the goods have been sold, the data stored in the IC chip is read by an interrogator. At this timing, the role of the IC tag is over.
In the throw-away IC tag whose role has been over, the data stored in the IC chip remains if nothing is done. Therefore, the control of the data stored in the IC chip of used IC tag is important. For example, there may be considered a case that the IC tag (which was fitted to a goods and used properly) is peeled from the goods, the data stored in the IC chip is read, and this data is used illegally. It may be also considered that the data stored in the IC chip of discarded IC tag is falsified for illegal use.
In order to prevent such illegal use, there is a proposal on a method of deactivating an IC tag by generating an induced current in the resonance circuit constituting the IC tag, by using a deactivation machine which generates a high-output electric field (JP-A-2002-185281, paragraph No. 0002). In this deactivation method, however, there is a case that the ability of communication with interrogator is restored by the restoration of resonance ability, after the deactivation treatment. Further, there is a problem that, in this deactivation method, visual confirmation of deactivation is impossible.
There is also a proposal on an IC tag obtained by forming, in the substrate having an electronic circuit of IC tag formed thereon, portions of different peeling strengths (JP-A-2000-57292, claim 1). With this IC tag, when it is adhered to a goods, used, and then peeled from the goods for recovery, the electronic circuit of IC tag is destroyed. In the method of deactivating this IC tag, the destruction of electronic circuit takes place owing to the difference in peeling strength; therefore, stable control of peeling strength is necessary. Further, there is required a step of forming a peeling layer, which increase the number of steps of IC tag production.